Case-mix adjustment is a critical component of outcomes analysis for ESRD patients. Previous efforts at case-mix modeling for ESRD patients have been limited by the number of data elements available for analysis, and methodologic differences in case-mix modeling have resulted in models of varying complexity. No comparisons of these models predictive power have been made. The goals of this proposal are to build upon the extensive case-mix severity experience of the Health Care Research Unit at Boston University Medical Center in order to: 1) develop improved case-mix severity models predicting mortality for hemodialysis patients, 2) to test whether the explanatory variables within the case-mix model differ depending on the specific mortality outcome examined, 3) cross validate these models, 4) compare these models with those described in the literature, and 5) apply these models to the question of whether mortality of black and white hemodialysis patients differ after adjusting for severity. The project will involve analysis of the USRDS Case Mix Severity Special Study hemodialysis patient database. Development of a case-mix model for patient mortality will be based on a four dimensional concept of case-mix severity; consisting of disease-specific severity, general physiologic status, comorbidity, and functional status. A split-sample technique will be used for model validation. Previous models will be statistically compared with our new models' ability to predict mortality. Finally, applicability of the case-mix model will be examined through an analysis of mortality differences among blacks and whites. In future studies, this type of model could be applied to the examination of outcomes such as mortality across alternative clinical sites and ESRD therapies.